Tape measures are often configured to receive a length of windable material having measuring gradations thereon, wound around a reel, so as to store the material in a compact form. The windable material may be unwound from the reel, for use thereof. While the windable material is generally in the form of a thin metal tape (including but not limited to a blade or measuring tape), other windable materials including measuring gradations may alternatively be utilized including but not limited to composite, or any other appropriate material). Accordingly, while such devices are commonly known in the art as “tape measures,” or “measuring tape rule devices,” it may be appreciated that while the windable material with gradations utilized therein may be referred to as “tape,” the material of the tape can be varied. While some tape measures are configured to be manually wound, other tape measures are configured as retractable, with a spring bias configured to wind the windable material into the tape measure. An example of this latter configuration of tape measure may be found in U.S. Pat. No. 6,643,947, incorporated herein by reference in its entirety.
In some tape rule devices, to support a spring torque that facilitates complete retraction, the spring may occupy more space (e.g., it may be wider or longer) than what is desired.
In some other tape measures, to ensure complete retraction of the windable material therein, the spring may require a large torque profile, which may overcome friction of the windable material as it winds onto the reel. For example, some windable materials of tape measures may generally have a concave configuration, so as to resist deformation along a length of the windable material as it is extended from the reel. As the windable material is further wound around the reel, the concave configuration in interior windings of the windable material may flatten due to the force applied from exterior windings of the windable material. Such flattening of the otherwise concave configuration may further cause frictional resistance to winding or unwinding the windable material. The longer the windable material extraction from a stored state, the more progressive the torque demand to retract the windable material around the reel, and the greater the spring torque profile required to ensure complete retraction. It may be appreciated that excessive spring torque beyond that required to overcome frictional resistance of the windable member may result in a higher retraction speed than what might be desired.
Among other things, the present application relates to an improved measuring tape design.